Hybrid-electric and hydrogen-based propulsion systems are considered important building blocks for the decarbonisation of aviation. Especially smaller aircraft are currently the subject of research and development due to lower performance and range requirements: on the one hand for demonstration and testing purposes, but on the other hand already with specific ambitions for market-ready products. As part of the Federal Aviation Research Programme, appropriate preliminary design methods for propulsion and aircraft have been developed in the project “Integrated assessment of electro-hybrid propulsion systems for small aircraft” (IVekLu).

The commercial GasTurb™ software was extended to include models for electric propulsion components, hydrogen-powered fuel cell systems, and liquid hydrogen tanks. Furthermore, methods for the design of thermal management systems for batteries have been developed. Due to the large amounts of heat to be dissipated, detailed modelling of these systems is important at the preliminary design stage. Moreover, the existing aircraft design processes have been extended to include methods to model relevant propulsion integration aspects. For example, hydrogen propulsion integration or the reflection of the aerodynamic propeller wing interaction have been addressed.

To demonstrate the developed methods, studies of two representative aircraft configurations have been conducted: a feeder aircraft with serial-hybrid powertrain and blown wing for nine passengers and a vertical take-off tiltrotor configuration with hydrogen fuel cell propulsion and boost batteries with four seats.

Research and development

Research and development activities in the field of small, conventional take-off and landing aircraft: In 45 % of the projects evaluated, an aircraft for commercial use is stated as the dedi- cated project goal.

Vertical take­off tiltrotor aircraft powered by hydrogen fuel cells

With liquid hydrogen as the main energy carrier, technology assumptions for 2035 enable ranges of 160 km and more. Boost batteries provide the high power for take-off and landing.
Despite a 42 % improvement in aerodynamic efficiency at cruise, no significant fuel savings could be obtained: The serial-hybrid powertrain results in a 43 % increase in empty weight.

Das zugrundeliegende Vorhaben wurde mit Mitteln des Bundesministeriums für Wirtschaft und Klimaschutz unter dem Förderkennzeichen 20Q1942B gefördert.